Applicant""s hereby claim the right of priority, under 35 U.S.C. xc2xa7119, based on Japanese Application No. 2000-047433, filed on Feb. 24, 2000, the entire contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention generally relates to a hybrid electric vehicle and more particularly to a generation control technique for a hybrid electric vehicle.
2. Description of Related Art
In recent years, there has been developed a series hybrid vehicle, equipped with a motor as a source of driving force for the vehicle and a secondary battery, which supplies power to the motor, charged by a generator driven by a relatively-small engine. Normally, the series hybrid vehicle operates the engine to run the generator in order to charge the battery if a charging level (SOC: state of charge) of the battery is low.
In this series hybrid type vehicle, however, a large amount of battery power may be consumed and rapidly lowers the charging level (SOC) of the battery if a motor is required to supply a high output, as in the case where a vehicle is running on an uphill slope or accelerating rapidly. In this case, the charging is delayed even if the generator is operated.
To address this problem, Japanese Patent Provisional Publication No. 11-103503, for example, discloses changing the generated power of a generator and the charged power of the battery according to the rate of change xcex94SOC of a battery remaining capacity to thereby stabilize the charge state of the battery.
According to the above publication, the rate of change xcex94SOC of the battery remaining capacity is detected. Thus, if the motor requires a high output, the power generated by the generator does not increase until the power of the battery is once used and lowers the charging level of the battery. More specifically, the generated power does not increase until a certain period of time has passed from a high output requirement from the motor.
If there is a delay from the time when the high output from the motor is required to the time when the battery is charged, the charge of the battery is significantly decreased and cause a deep discharge until the increase in the generated power is corrected. During this period, it is impossible to achieve a desired motor output according to the high output requirement. This is undesirable because a driver feels a sense of incongruity.
Moreover, the deep discharge may deteriorate the charging and discharging efficiency of the battery.
It is therefore an object of the present invention to provide a generation control device of a hybrid electric vehicle, which is able to satisfactorily generate power with an excellent responsiveness with respect to a high output requirement from a motor.
The above object can be accomplished by providing a hybrid electric vehicle comprising: a battery; a generator being rotated by a driving force of an engine to generate power to charge the battery; a traction motor being run by power of the battery; a required power consumption sensing device for sensing a required power consumption of the traction motor; a charge level sensing device for sensing a charge level of the battery; and a generated power control device that starts a normal output generation by said generator if the charge level sensed by the charge level sensing device is not greater than a generation start value, continues the normal output generation until the charge level reaches a generation end value larger than the generation start value, and performs a high output generation with a higher output than in the normal output generation regardless of the charge level sensed by the charging level sensing device if the required power consumption sensed by the required power consumption sensing device is not less than a set value.